New systematic review methodology for visual impairment and blindness for the 2010 Global Burden of Disease study

Abstract

Purpose: To describe a systematic review of population-based prevalence studies of visual impairment (VI) and blindness worldwide over the past 32 years that informs the Global Burden of Diseases, Injuries and Risk Factors Study.

Methods: A systematic review (Stage 1) of medical literature from 1 January 1980 to 31 January 2012 identified indexed articles containing data on incidence, prevalence and causes of blindness and VI. Only cross-sectional population-based representative studies were selected from which to extract data for a database of age- and sex-specific data of prevalence of four distance and one near vision loss categories (presenting and best-corrected). Unpublished data and data from studies using rapid assessment methodology were later added (Stage 2).

Results: Stage 1 identified 14,908 references, of which 204 articles met the inclusion criteria. Stage 2 added unpublished data from 44 rapid assessment studies and four other surveys. This resulted in a final dataset of 252 articles of 243 studies, of which 238 (98%) reported distance vision loss categories. A total of 37 studies of the final dataset reported prevalence of mild VI and four reported near VI.

Conclusion: We report a comprehensive systematic review of over 30 years of VI/blindness studies. While there has been an increase in population-based studies conducted in the 2000s compared to previous decades, there is limited information from certain regions (eg, Central Africa and Central and Eastern Europe, and the Caribbean and Latin America), and younger age groups, and minimal data regarding prevalence of near vision and mild distance VI.

Figure 1

Flow Diagram detailing the stages of the systematic review

Figure 2

Data availability plot for studies conducted between 1980 and 2012, identified by the GBD Study systematic review that reported distance visual acuity sequelae, organised by region, with survey year and population-representativeness highlighted. The population sampled by each study is represented as either national in scope, that of a first administrative unit or greater (includes state or regional) or a local/district level.